Infrared Extinction Properties of Nanostructured and Conventional Particles

Abstract

Brass flakes and carbon-based particulates are effective obscurants in the infrared (IR) region of the electromagnetic spectrum; however, they are toxic and can cause respiratory problems and environmental concerns. There is a need to develop or identify nontoxic IR obscurants. This research was conducted to determine the potential of nanostructured particles as IR obscurants. Three commercial nanostructured particles were compared with two conventional particles and common obscurants. Experiments involved dispersing a known mass of particles into a particle chamber and measuring the IR transmission through the chamber with a Fourier transform infrared analyzer and the mass concentration with filter samplers. The size distribution of the aerosolized particles was also measured with an aerodynamic particle sizer spectrometer. From the measured data, the mean values of the mass extinction coefficient, σ_m, and volume extinction coefficient, σ_v, for the spectral bands of interest (i.e., 3–5 μm and 8–12 μm) were calculated. Results showed that ISO fine test dust, NaHCO₃ and NanoActive TiO₂ (for 3–5 μm) appeared to be the most promising alternatives to brass or graphite flakes. By manipulating the size and/or morphology of these particles, it might be possible to enhance their IR extinction performance.

Keywords:

• extinction coefficient
• Fourier transform infrared (FTIR)
• infrared
• nanostructured particles
• obscurant

Acknowledgments

This work was funded by the United States Marine Corps Systems Command through M2 Technologies, Inc. The technical assistance provided by Dr. Larry Erickson, Darell Oard, Edna Razote, Emad Almuhanna, Kevin Hamilton, Tyler Pjesky, Blase Leven, and Ryan Green is acknowledged. Contribution no. 09-075-J from Kansas Agricultural Experiment Station.

Notes

^a Source: NanoScale Materials, Inc., Manhattan, KS.

^b Source: Amerex Corp., Trussville, AL.

^c Source: PTI Powder Technolgy, Inc., Burnville, MN.

^d Source: Wolstenholme International Inc., Chicago, IL.

^e Source: Asbury Graphite Mills, Inc., Asbury, NJ.

^f Measured using multipyenometer.

^a Column means followed by the same letter are not significantly different at the 5% level.

^a Column means followed by the same letter are not significantly different at the 5% level.

^a Column means followed by the same letter are not significantly different at the 5% level.